Breathing fresh life into old buses

7th August 2017

Case studies

Increasingly stringent emissions targets and local regulations are drawing attention to the polluting effect of local public transport systems. Working in partnership with Transport for London, we developed a cost effective catalysts and filter system to remove harmful gases and particulates, which can be retrofitted to the bus exhaust system without having to scrap the old vehicles.

Inspiring science

A precious metal catalyst (usually containing platinum and palladium), converts harmful carbon monoxide and hydrocarbons into carbon dioxide and water. In conjunction with this, another catalyst typically using base metals such as vanadium, copper or iron, converts oxides of nitrogen, or NOx, to nitrogen. Each installation required fine tuning and careful testing on each type of vehicle. Between these catalysts, a diesel particulate filter traps and then combusts very small soot particles, preventing them from leaving the exhaust. The process of developing effective catalysts for London's fleet of retrofitted buses involves the application of precise science, including a system for injecting low levels of ammonia to react with emissions as they pass through the catalyst.

Market application

Using this technology, we can take a twelve year old bus and achieve exhaust emission levels comparable to a modern bus. Approximately 15 older buses can be retrofitted for less than the cost of buying a brand new model, conserving natural resources, reducing fleet costs, and minimising environmental impact. So far, retrofitting projects have been successfully completed with partners in many parts of the world including Spain, Belgium, Denmark, Sweden, Hong Kong, and the UK.

Making a difference to lives

We are now working on meeting the latest clean air threshold as defined by EU regulations known as Euro VI. London has a stated objective of achieving an ultra-low emission zone at its heart by 2019, and Johnson Matthey and its partners have already demonstrated the latest technology is capable of meeting this stringent standard, helping city dwellers breathe easier.